Process for making photographic films



United States Patent 3,454,424 PROCESS FOR MAKING PHOTOGRAPHIC FILMSRudolf Schneider, Neu-Isenburg, Germany, assignor to E. I. du Pont deNemours and Company, Wilmington, Del.,' a corporation of Delaware NoDrawing. Filed June 21, 1966, Ser. No. 559,082 Claims priority,applicatiog Germany, July 30, 1965,

88 Int. Cl. B32b 32/12,27/06,- G03c N78 US. Cl. 117-145 5 ClaimsABSTRACT OF THE DISCLOSURE This invention pertains to a process formaking dimensionally stable photographic films having a support composedof organic cellulose esters.

It is known that photographic films undergo dimensional changes underthe influence of varying atmospheric conditions. Dimensional variationsalso occur in processing photographic films, even under constantatmospheric conditions. Under the effects, usually rather prolonged, ofaqueous and sometimes strongly alkaline processing baths thephotographic film first swells, only to shrink again during thesubsequent drying process. The dimensional changes involved here areirreversible, i.e. the initial dimensions of the photographic film arenot regained but instead permanent dimensional changes occur. Forexample, it can usually be observed that photographic films have shrunk,as compared with their initial state at the instant of exposure, afterthe developing and drying processes.

For many types of photographic films, especially in copying methods,aerial photography and others, dimensional stability of the photographicfilm is important.

The film base itself is the controlling factor for the dimensionalstability of the coated photographic films. The photosensitive layer,however, has some influence, especially on dimensional changes whichoccur during processing of the coated film. As applicants have been ableto demonstrate, this is particularly true of the type of film supportingtreatment, the solvent employed in applying the film support having inparticular a substantial influence. Efforts have been made to improvedimensional stability of photographic films by using stronglyhydrophobic plastic film base. In this respect, the best dimensionalstability is obtained with hydrophobic film base made from polyesters ofterephthalic acid with ethylene glycol, and by polystyrene orpolycarbonate films.

Nevertheless, it is known that dimensional stability of such hydrophobicfilm bases can be implemented only if they are coated withphotosensitive emulsions in which at least a part of the gelatin hasbeen replaced by synthetic plastics. Such a replacement of gelatinsometimes has, on the other hand, a highly unfavorable effect on thephotographic properties of the emulsions, so that for the sake ofphotographic quality of the product the ultimate choice is to acceptdecreased dimensional stability as compared with the uncoated foil.Because of this and other disadvantages, such as difliculties inpreparation and in ice subbing the film support, film bases composed oforganic cellulose esters, e.g. cellulose acetate, cellulose propionate,cellulose acetate/propionate, and cellulose acetate/butyrate, andespecially cellulose triacetate, still constitute commercially usefulbases for many purposes.

A requirement which organic cellulose ester films are still unable tomeet fully, in spite of their excellent mechanical properties, is theextraordinary demand imposed by modern copying techniques on dimensionalstability of film supports. For example, photographic film having acellulose triacetate base undergoes, during the various stages ofpreparation and processing under constant atmospheric conditions changesin length as set forth in Table I below, wherein a negative sign meansthat the film has shrunk while a positive sign indicates that thefinished processed film has increased in length.

TABLE I Percent change in film length Film preparation stage: caused byprocessing Cellulose triacetate film support not substrate treatedl+0.030 Cellulose triacetate film support treated with a substratesolution from the prior art, containing gelatin -0.-070 Cellulosetriacetate film support, coated as in the prior art and coated with aphotosensitive silver halide emulsion 0.l00

As may be seen from Table I, only the substrate treatment by itselfcauses a change of 0.100% in dimensional stability whereas applicationof the photosensitive layer merely causes an additional 0.030% ofshrinkage.

Now it has been found that this decrease in dimensional stability toprocessing, caused by the substrate treatment in organic cellulose esterfilm bases can be prevented by using as subbing solution for the filmsupport a solvent blend of ethyl acetate and isopropanol, and as theadhesive copolymers of maleic anhydride with other polymerizablemonomers containing vinyl groups which are not substituted on thea-carbon atom of the vinyl group. Suitable such copolymers are disclosedin German Patent 1,040,898.

A photosensitive film, containing a subbing layer, prepared from maleicanhydride copolymer and the above mentioned solvents undergoessubstantially no dimensional change in processing baths and ischaracterized by excellent dimensional stability. Table II shows theimprovement in dimensional stability to processing in finished,emulsion-coated films obtained in accordance with this invention.

TABLE II Percent change in film length, Film preparation stage: causedby processing Cellulose triacetate film support, untreated ,-|-0.30Cellulose triacetate film support, prepared for substrate in accordancewith this invention ;+0.025 Cellulose triacetate film support, preparedfor substrate in accordance with this invention and emulsion-coated0.005

Thus it is possible, according to this invention, to effect animprovement in dimensional stability to processing in photographic filmshaving an organic cellulose ester film support, especially cellulosetriacetate, that the dimensional change occurring after processing isless than i0.01%.

In addition to their beneficial effect on dimensional stability toprocessing, substrate layers made in accordance with this invention areexcellent adhesive agents between the film support and thephotosensitive emulsion, and in 3 other respects also they meet allrequirements which these layers must satisfy.

The optimum adhesive effect and dimensional stability is attained ingeneral when use is made of a solvent blend of 5080% ethyl acetate and50-20% isopropanol.

It is completely unexpected and in no Way obvious to one skilled in theart that by using the disclosed maleic anhydride copolymers and ethylacetate and isopropanol as the solvent blend, one can obtain animprovement in dimensional stability to processing in the finished filmproduct. That this result is surprising is evidenced by the fact that ifethyl acetate and/ or isopropanol are replaced by other solvents, e.g.,acetone and/ or methanol, customarily used for coating copolymer subbinglayers in making photographic film base, dimensional stability isseriously impaired.

Corresponding comparative tests gave the results set forth in thefollowing table:

TABLE III Example A cellulose triacetate foil, 140 microns thick,consisting of 100 parts cellulose triacetate (acetic acid content 61.0%)and parts triphenyl phosphate, prepared from a solution of thesesubstances in methylene chloride:

Percent change in length by processing a film made by applying asubstrate solution containing the solvent blends- 50-80% EtOAc, 50-s0%MezCO 50-80% EtOAc, 50-80% MezCO,

-40% EtOAc, 25-40% MGZCO,

Film base MezCHOH MegCHOH MeOH MeOH 50-20% MeOH Cellulose triacetatefilm support not substrate treated +0. 030 Cellulose triacetate filmbase substrate treated with solvent blends +0. 025 0. 020 +0. 005 0. 050-0. 025 Cellulose triacetate film base substrate treatment as indicatedcoated with a gelatin-silver halide emulsion 0. 005 0. 050 0. 025 0. 0800. 055

As may be determined from Table 'III, wherein Me is methyl, Et is ethyland Ac is CH COO, the improvement in dimensional stability to processingis attained only when the maleic anhydride copolymer is applied from asolvent blend, e.g. ethyl acetate and isopropanol, in accordance withthis invention.

It should be recognized that it is impossible to prepare stablegelatin-containing substrate solutions in absence of Water, using onlyethyl acetate and isopropanol, so that the observation underlying thepresent invention could not have been determined from a simpleconversion of a classical substrate preparation method to the basis ofusing gelatin.

Suitable copolymers for carrying out the process as disclosed arechiefly those made from maleic anhydride and vinyl acetate, the twocomponents being employed preferably in approximately equivalentquantities. There are, however, other copolymers, e.g. those made frommaleic anhydride and vinylmethyl ether or styrene, or also, moreespecially, from vinyl chloroacetate or ethene or the like, which arewell suited.

The copolymers can be made by known processes. For example, the monomermixture of maleic anhydride and vinyl acetate in the mole ratio 1:1 maybe polymerized at 80 C. in benzene solution, using peroxide catalysts,e.g. benzoyl peroxide. The reaction product precipitates in finelypowdered form. If desired, there may be added to the batch, afterpolymerization is complete, a precipitating agent such as diethyl ether,and the polymer may be separated from the solvent by filtering. Usuallyno further purification is needed. The copolymers are applied to thefilm support in the customary manner from solutions containing 0.5 to3.0% of the respective copolymers, and may be dried and wound up by theusual method. Film bases pretreated in this way may then be coated witha photosensitive emulsion by any of the customary methods.

By the process according to this invention the dimensional stability toprocessing in photographic films with methanol 9:1 parts by volume, istreated on both sides by a prior art procedure using a substratesolution of the composition:

Parts Vinyl acetate/maleic anhydride copolymer mole ratio 1:1 1.0 Ethylacetate 71.0 Isopropanol 28.0

and is dried (Sample A, process according to this invention).

A second specimen of the cellulose triacetate foil designated above istreated with a substrate solution from the prior art, having thecomposition:

Parts Gelatin 0.8 Acetic acid 0.8 Water 16.8 Methanol 15.0 Isopropanol8.6 Acetone 58.0

and is dried (Sample B, prior art process).

Both film supports are then coated on one side with an antihalationlayer of gelatin and a suitable antihalation dye, and on the other sidewith a photosensitive gelatinsilver halide emulsion layer having thefollowing properties:

AgClzAgBr ratio 2:1 Gelatinzsilver halide ratio 1:1 Applied silverhalide g./ sq. m 10 and after developing. The differences between thetwo measurements, which indicate the changes in film length due to theprocessing, are shown in the following table:

By substituting the other specific cellulose ester film bases that aredescribed above, similar results can be obtained.

As may be seen, the material prepared in accordance with this inventionundergoes substantially no dimensional change during its processing inthe photographic baths, unlike the material made with a film basetreated for substrate according to the prior art.

I claim:

1. A process for making dimensionally stable organic cellulosemonocarboxylic acid ester photographic film base which comprisesapplying to the film base an adhesive sublayer from a solution of acopolymer of one mole of maleic anhydride with one mole of a difierentaddition polymerizable ethylenically unsaturated monomer containing avinyl group not substituted at the a-carbon atom of the vinyl group in asolvent blend of 50%-80% ethyl acetate and 50%20% isopropanol, by weightand drying the treated film base.

2. A process according to claim 1, characterized in that a copolymer ofmaleic anhydride and vinyl acetate is employed.

3. A process according to claim 1, characterized in that a copolymer ofmaleic anhydride and vinyl chloroacetate is employed.

4. A process according to claim 1 wherein said cellulose ester iscellulose triacetate.

5. A process according to claim 1 wherein said cellulose ester iscellulose acetate/butyrate.

References Cited UNITED STATES PATENTS 2,067,706 1/ 1937 Fikentscher260-861 2,562,853 7/1951 Baer 260-785 2,637,712 5/1953 Upton 260-785 X2,756,163 7/ 1956 Herrick et al.

2,772,972 12/1956 Herrick et al. 96-75 X 3,072,482 1/-l963 Beeber et al.9675 3,130,051 4/1964 Herrick et a1 96-91 X 3,227,555 1/1'966 Norman9687 X 3,228,768 1/ 1966 Straw et al. 9675 X 5 WILLIAM D. MARTIN,Primary Examiner.

M. LUSIGNAN, Assistant Examiner.

US. Cl. X.R.

